High-resolution seismic imaging of fluid escape structures in the North Sea

One approach to mitigating climate change associated with burning fossil fuels is to store the resulting carbon dioxide (CO2) beneath the seabed, for example in former gas reservoirs beneath the North Sea. It is important that such storage sites do not leak, so it is important also to build an understanding of how such leakage can occur. The location of CO2 leakage and the potential intensity of CO2 leakage at the seafloor are critically dependent on the distribution of fluid pathways and on the permeability of these pathways. So-called “chimney” structures, that cross-cut the sediment layering, may represent such pathways. Often these structures are linked to depressions on the seabed that can reach hundreds of metres in diameter and are called “pockmarks”. Natural gas is likely to have migrated through the chimneys into the water column at some point in geological time. In the summer of 2017 a unique seismic dataset has been acquired at the Scanner pockmark complex (northern North Sea), which is actively venting gas. The aim of this project is to apply novel analysis techniques to a subset of these data in order to determine their three-dimensional structure and physical properties controlling fluid flow at high resolution.

The student will have access to three-dimensional seismic tomographic and seismic reflection datasets acquired over the pockmark and its surroundings using a variety of sources as part of the NERC-funded CHIMNEY project. The project will involve:

Reprocessing existing industry 3D seismic data to optimize resolution of shallow structures.
Comparison of the reprocessed dataset with 2D and pseudo-3D seismic reflection data acquired with higher-frequency sources.
Application of novel approaches such as interferometry, guided and Scholte wave analysis, mirror imaging and full-waveform inversion, to multi-frequency ocean bottom seismic data.
Comparison of structures with those observed at fluid escape structures elsewhere in the North Sea and globally.
Project work is likely to involve some collaboration with CHIMNEY Project Partner CGG.

The SPITFIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted in Ocean and Earth Science. Specific training will include participation in seismic data acquisition at sea; the opportunity to attend high-level courses in seismic data analysis; training in high-performance computing; and training in state-of-the-art marine seismic data analysis techniques. The project will involve interaction with other scientists in the UK and Germany who are involved in the wider CHIMNEY and STEMM-CCS projects; through this interaction the student will develop strong communication and team-working skills.